The present invention relates to rotary compressors or blowers, particularly to blowers of the Roots type. More specifically, the present invention relates to a rotor, shaft, and gear arrangement for a Roots-type blower which functions as a supercharger for an internal combustion engine.
Rotary blowers, particularly Roots-type blowers, employed as superchargers for internal combustion engines are well-known in the prior art. However, they have not been widely used, particularly in passenger cars for several reasons since they, in general, have been characterized by problems such as noisy operation, expensive machining and assembly, low efficiency, and poor durability. The noisy operation may be roughly classified into two groups: a solidborne noise caused by rotation of timing gears and rotor shaft bearings, and fluid-borne noise believed to be, in part, caused by the siren-effect of the rotors and reverse flow of fluid at the blower outlet. Herein is disclosed an improved bearing arrangement which not only reduces bearing noise and improves bearing life but which also, in combination with other features disclosed herein, reduces the blower manufacturing cost, improves efficiency, and improves durability.
Prior art rotary blowers of the general type disclosed herein require close tolerance machining of parts and meticulous adjustment during assembly to ensure noncontact of the rotors with housing wall surfaces defining the chambers they are disposed in and to ensure noncontact of the meshing lobes of the rotors. Herein is disclosed an improved rotor, shaft, and timing gear design which reduces machining and assembly costs, and which facilitates the use of minimum running clearances between the rotor and housing surfaces and between the meshed lobes of the rotors. Further, the disclosed bearing arrangement and design of the rotor, shaft, timing gears combine to improve the blower efficiency and durability.